Ophthalmic lenses, such as hydrogel contact lenses are formed, inspected, and packaged on manufacturing lines with minimal human intervention. During these processes, certain defects to those lenses occur and one common defect is missing material in a formed lens. Whether such missing material is the entire thickness of a contact lens, or just a portion of its thickness, lenses with such defects should be removed from the product that ultimately reaches end users.
There are inspection methods, which find holes in ophthalmic lenses. However, given the variety of different types of contact lens materials that are on the market, lens makers often must inspect such lenses using radiation of different wavelengths. This is particularly true if one is looking for a missing material defect which is not a complete hole, such as a depression in the lens material. Typically the process of finding radiation of an optimal wavelength is a trial and error process. This trial and error method wastes a great deal of time and materials, and does not guarantee an optimal wavelength selection. Therefore, it is desirable to determine the optimal wavelength of radiation for the inspection of such missing material defects without a trial and error process. This desire is met by the foregoing invention.